From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E146ECDFB1 for ; Fri, 13 Jul 2018 20:40:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9A172075B for ; Fri, 13 Jul 2018 20:40:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C9A172075B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732677AbeGMU4T (ORCPT ); Fri, 13 Jul 2018 16:56:19 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59840 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731895AbeGMU4T (ORCPT ); Fri, 13 Jul 2018 16:56:19 -0400 Received: from akpm3.svl.corp.google.com (unknown [104.133.9.92]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id A28EACF7; Fri, 13 Jul 2018 20:40:04 +0000 (UTC) Date: Fri, 13 Jul 2018 13:40:02 -0700 From: Andrew Morton To: Naoya Horiguchi Cc: linux-mm@kvack.org, Michal Hocko , xishi.qiuxishi@alibaba-inc.com, zy.zhengyi@alibaba-inc.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/2] mm: soft-offline: close the race against page allocation Message-Id: <20180713134002.a365049a79d41be3c28916cc@linux-foundation.org> In-Reply-To: <1531452366-11661-3-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1531452366-11661-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1531452366-11661-3-git-send-email-n-horiguchi@ah.jp.nec.com> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 13 Jul 2018 12:26:06 +0900 Naoya Horiguchi wrote: > A process can be killed with SIGBUS(BUS_MCEERR_AR) when it tries to > allocate a page that was just freed on the way of soft-offline. > This is undesirable because soft-offline (which is about corrected error) > is less aggressive than hard-offline (which is about uncorrected error), > and we can make soft-offline fail and keep using the page for good reason > like "system is busy." > > Two main changes of this patch are: > > - setting migrate type of the target page to MIGRATE_ISOLATE. As done > in free_unref_page_commit(), this makes kernel bypass pcplist when > freeing the page. So we can assume that the page is in freelist just > after put_page() returns, > > - setting PG_hwpoison on free page under zone->lock which protects > freelists, so this allows us to avoid setting PG_hwpoison on a page > that is decided to be allocated soon. > > > ... > > + > +#ifdef CONFIG_MEMORY_FAILURE > +/* > + * Set PG_hwpoison flag if a given page is confirmed to be a free page > + * within zone lock, which prevents the race against page allocation. > + */ I think this is clearer? --- a/mm/page_alloc.c~mm-soft-offline-close-the-race-against-page-allocation-fix +++ a/mm/page_alloc.c @@ -8039,8 +8039,9 @@ bool is_free_buddy_page(struct page *pag #ifdef CONFIG_MEMORY_FAILURE /* - * Set PG_hwpoison flag if a given page is confirmed to be a free page - * within zone lock, which prevents the race against page allocation. + * Set PG_hwpoison flag if a given page is confirmed to be a free page. This + * test is performed under the zone lock to prevent a race against page + * allocation. */ bool set_hwpoison_free_buddy_page(struct page *page) { > +bool set_hwpoison_free_buddy_page(struct page *page) > +{ > + struct zone *zone = page_zone(page); > + unsigned long pfn = page_to_pfn(page); > + unsigned long flags; > + unsigned int order; > + bool hwpoisoned = false; > + > + spin_lock_irqsave(&zone->lock, flags); > + for (order = 0; order < MAX_ORDER; order++) { > + struct page *page_head = page - (pfn & ((1 << order) - 1)); > + > + if (PageBuddy(page_head) && page_order(page_head) >= order) { > + if (!TestSetPageHWPoison(page)) > + hwpoisoned = true; > + break; > + } > + } > + spin_unlock_irqrestore(&zone->lock, flags); > + > + return hwpoisoned; > +} > +#endif